Skin cancers (skin neoplasms) are named after the type of skin cell from which they arise. Basal cell cancer originates from the lowest layer of the epidermis, and is the most common but least dangerous skin cancer.
Squamous cell cancer originates from the middle layer, and is less common but more likely to spread, and if left untreated, becomes fatal. Melanoma, which originates in the pigment-producing cells (melanocytes), is the least common but most aggressive, most likely to spread, and if untreated, becomes fatal.
While most cases are caused by over-exposure to UV rays from the sun or sunbeds, treatment is generally via surgical removal.
There are a variety of different skin cancer symptoms. These include changes in the skin that do not heal, ulcering in the skin, discolored skin, and changes in existing moles, such as jagged edges to the mole and enlargement of the mole.
Ultraviolet radiation from exposure to sunlight is the primary cause of skin cancer. Other factors that play a role include:
HPV infections increase the risk of squamous cell carcinoma.
Some genetic syndromes, including congenital melanocytic nevi syndrome, which is characterised by the presence of nevi (birthmarks or moles) of varying size which are either present at birth, or appear within 6 months of birth. Nevi larger than 20 mm (3/4") in size are at higher risk of becoming cancerous.
Chronic non-healing wounds. These are called Marjolin's ulcers based on their appearance, and can develop into squamous cell carcinoma.
Ionising radiation, environmental carcinogens, artificial UV radiation (e.g. tanning beds), aging, and light skin colour. It is believed that tanning beds are the cause of hundreds of thousands of basal and squamous cell carcinomas. The World Health Organisation now places people who use artificial tanning beds in its highest risk category for skin cancer.
The use of many immunosuppressive medication increases the risk of skin cancer. Cyclosporin A, a calcineurin inhibitor, for example, increases the risk by approximately 200 times, and azathioprine about 60 times.
Treatment is dependent on type of cancer, location of the cancer, age of the patient, and whether the cancer is primary or a recurrence. Treatment is also determined by the specific type of cancer.
For a small basal cell cancer in a young person, the treatment with the best cure rate (Mohs surgery or CCPDMA) might be indicated. In case of an elderly frail man with multiple complicating medical problems, a difficult to excise basal cell cancer of the nose might warrant radiation therapy (slightly lower cure rate) or no treatment at all.
Topical chemotherapy might be indicated for large superficial basal cell carcinoma for good cosmetic outcome, whereas it might be inadequate for invasive nodular basal cell carcinoma or invasive squamous cell carcinoma. In general, melanoma is poorly responsive to radiation or chemotherapy.